Regular modifier checker implemented (initial version). A set of tests fixed accordingly.

Most of modifier diagnostic is expressed by REDUNDANT_MODIFIER, INCOMPATIBLE_MODIFIERS, REPEATED_MODIFIER, WRONG_MODIFIER_TARGET, WRONG_MODIFIER_PARENT.
A set of modifier diagnostics is not in use now (but not deleted yet).

compiler/testData/codegen/box/classes/delegation4.kt

@@ -1,8 +1,8 @@
-open interface First {
+interface First {
   public open fun foo() : Int
 }
 
-open interface Second : First {
+interface Second : First {
   public open fun bar() : Int
 }